From: Dave Chinner <dchinner@xxxxxxxxxx>
The current xfs_file_aio_write code is a mess of locking shenanigans
to handle the different locking requirements of buffered and direct
IO. Start to clean this up by disentangling the direct IO path from
the mess.
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/linux-2.6/xfs_file.c | 184 +++++++++++++++++++++++++++---------------
1 files changed, 118 insertions(+), 66 deletions(-)
diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
index 4608aab..d70a249 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -587,6 +587,116 @@ out_lock:
return error;
}
+/*
+ * xfs_file_dio_aio_write - handle direct IO writes
+ *
+ * Lock the inode appropriately to prepare for and issue a direct IO write.
+ * By spearating it from the buffered write path we remove all the tricky to
+ * follow locking changes and looping. This also clearly indicates that XFS
+ * does not fall back to buffered IO in the direct IO write path.
+ *
+ * Returns with locks held indicated by @need_i_mutex and @iolock.
+ */
+STATIC ssize_t
+xfs_file_dio_aio_write(
+ struct kiocb *iocb,
+ const struct iovec *iovp,
+ unsigned long nr_segs,
+ loff_t pos,
+ size_t ocount,
+ int *need_i_mutex,
+ int *iolock)
+{
+ struct file *file = iocb->ki_filp;
+ struct address_space *mapping = file->f_mapping;
+ struct inode *inode = mapping->host;
+ struct xfs_inode *ip = XFS_I(inode);
+ struct xfs_mount *mp = ip->i_mount;
+ ssize_t error = 0;
+ xfs_fsize_t new_size;
+ size_t count = ocount;
+ xfs_buftarg_t *target = XFS_IS_REALTIME_INODE(ip) ?
+ mp->m_rtdev_targp : mp->m_ddev_targp;
+
+ *need_i_mutex = 0;
+ *iolock = 0;
+ if ((pos & target->bt_smask) || (count & target->bt_smask))
+ return XFS_ERROR(-EINVAL);
+
+ if (mapping->nrpages || pos > ip->i_size) {
+ *iolock = XFS_IOLOCK_EXCL;
+ *need_i_mutex = 1;
+ mutex_lock(&inode->i_mutex);
+ } else {
+ *iolock = XFS_IOLOCK_SHARED;
+ }
+ xfs_ilock(ip, XFS_ILOCK_EXCL|*iolock);
+
+ error = generic_write_checks(file, &pos, &count,
+ S_ISBLK(inode->i_mode));
+ if (error) {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL|*iolock);
+ *iolock = 0;
+ return error;
+ }
+
+ new_size = pos + count;
+ if (new_size > ip->i_size)
+ ip->i_new_size = new_size;
+
+ if (likely(!(file->f_mode & FMODE_NOCMTIME)))
+ file_update_time(file);
+
+ /*
+ * If the offset is beyond the size of the file, we have a couple of
+ * things to do. First, if there is already space allocated we need to
+ * either create holes or zero the disk or ...
+ *
+ * If there is a page where the previous size lands, we need to zero it
+ * out up to the new size.
+ */
+ if (pos > ip->i_size) {
+ error = -xfs_zero_eof(ip, pos, ip->i_size);
+ if (error) {
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+ }
+ }
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+ /*
+ * If we're writing the file then make sure to clear the setuid and
+ * setgid bits if the process is not being run by root. This keeps
+ * people from modifying setuid and setgid binaries.
+ */
+ error = file_remove_suid(file);
+ if (unlikely(error))
+ return error;
+
+ if (mapping->nrpages) {
+ WARN_ON(*need_i_mutex == 0);
+ error = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1,
+ FI_REMAPF_LOCKED);
+ if (error)
+ return error;
+ }
+
+ if (*need_i_mutex) {
+ /* demote the lock now the cached pages are gone */
+ xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
+ mutex_unlock(&inode->i_mutex);
+ *iolock = XFS_IOLOCK_SHARED;
+ *need_i_mutex = 0;
+ }
+
+ trace_xfs_file_direct_write(ip, count, iocb->ki_pos, 0);
+ error = generic_file_direct_write(iocb, iovp,
+ &nr_segs, pos, &iocb->ki_pos, count, ocount);
+
+ /* No fallback to buffered IO on errors for XFS. */
+ return error;
+}
+
STATIC ssize_t
xfs_file_aio_write(
struct kiocb *iocb,
@@ -628,19 +738,17 @@ xfs_file_aio_write(
if (XFS_FORCED_SHUTDOWN(mp))
return -EIO;
-relock:
if (ioflags & IO_ISDIRECT) {
- iolock = XFS_IOLOCK_SHARED;
- need_i_mutex = 0;
- } else {
- iolock = XFS_IOLOCK_EXCL;
- need_i_mutex = 1;
- mutex_lock(&inode->i_mutex);
+ ret = xfs_file_dio_aio_write(iocb, iovp, nr_segs, pos,
+ ocount, &need_i_mutex, &iolock);
+ goto done_io;
}
+ iolock = XFS_IOLOCK_EXCL;
+ need_i_mutex = 1;
+ mutex_lock(&inode->i_mutex);
xfs_ilock(ip, XFS_ILOCK_EXCL|iolock);
-start:
error = -generic_write_checks(file, &pos, &count,
S_ISBLK(inode->i_mode));
if (error) {
@@ -648,26 +756,6 @@ start:
goto out_unlock_mutex;
}
- if (ioflags & IO_ISDIRECT) {
- xfs_buftarg_t *target =
- XFS_IS_REALTIME_INODE(ip) ?
- mp->m_rtdev_targp : mp->m_ddev_targp;
-
- if ((pos & target->bt_smask) || (count & target->bt_smask)) {
- xfs_iunlock(ip, XFS_ILOCK_EXCL|iolock);
- return XFS_ERROR(-EINVAL);
- }
-
- if (!need_i_mutex && (mapping->nrpages || pos > ip->i_size)) {
- xfs_iunlock(ip, XFS_ILOCK_EXCL|iolock);
- iolock = XFS_IOLOCK_EXCL;
- need_i_mutex = 1;
- mutex_lock(&inode->i_mutex);
- xfs_ilock(ip, XFS_ILOCK_EXCL|iolock);
- goto start;
- }
- }
-
new_size = pos + count;
if (new_size > ip->i_size)
ip->i_new_size = new_size;
@@ -706,44 +794,7 @@ start:
/* We can write back this queue in page reclaim */
current->backing_dev_info = mapping->backing_dev_info;
- if ((ioflags & IO_ISDIRECT)) {
- if (mapping->nrpages) {
- WARN_ON(need_i_mutex == 0);
- error = xfs_flushinval_pages(ip,
- (pos & PAGE_CACHE_MASK),
- -1, FI_REMAPF_LOCKED);
- if (error)
- goto out_unlock_internal;
- }
-
- if (need_i_mutex) {
- /* demote the lock now the cached pages are gone */
- xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
- mutex_unlock(&inode->i_mutex);
-
- iolock = XFS_IOLOCK_SHARED;
- need_i_mutex = 0;
- }
-
- trace_xfs_file_direct_write(ip, count, iocb->ki_pos, ioflags);
- ret = generic_file_direct_write(iocb, iovp,
- &nr_segs, pos, &iocb->ki_pos, count, ocount);
-
- /*
- * direct-io write to a hole: fall through to buffered I/O
- * for completing the rest of the request.
- */
- if (ret >= 0 && ret != count) {
- XFS_STATS_ADD(xs_write_bytes, ret);
-
- pos += ret;
- count -= ret;
-
- ioflags &= ~IO_ISDIRECT;
- xfs_iunlock(ip, iolock);
- goto relock;
- }
- } else {
+ if (!(ioflags & IO_ISDIRECT)) {
int enospc = 0;
ssize_t ret2 = 0;
@@ -767,6 +818,7 @@ write_retry:
current->backing_dev_info = NULL;
+done_io:
xfs_aio_write_isize_update(inode, &iocb->ki_pos, ret);
error = -ret;
--
1.7.2.3
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